Method for operating an air conditioning system

ABSTRACT

In a method for operating a climate control system in a passenger compartment of a motor vehicle, the climate control system can be operated in a recirculation mode in which recirculated air is supplied to the passenger compartment or in fresh air mode in which at least a portion of the air supplied to the passenger compartment is fresh air. In its normal operating mode the climate control system is operated in recirculation mode. Upon exceeding a predetermined CO 2 -threshold value measured in the passenger compartment of the motor vehicle the climate control system is switched to fresh air mode.

BACKGROUND OF THE INVENTION

1. Field of the invention

The invention concerns a process for operating an air conditioning system in the passenger compartment of a motor vehicle of the generic type described in the pre-characterizing portion of claim 1. The invention further concerns an air conditioning system for a motor vehicle according to the pre-characterizing portion of claim 6.

2. Related Art of the Invention

Generic processes for operating air conditioning systems are known from the general state of the art. In normal operation the air conditioning system is operated in the recirculation mode, so that internal air is essentially recirculated within the passenger compartment of the motor vehicle and no fresh air is introduced. This has the advantage, in particular in the case of high ambient temperatures, that is in the cooling operation of the air conditioning system the air need not be cooled as strongly and the air conditioning system thus consumes less energy in the form of fuel. In order to nevertheless provide the vehicle occupants with fresh air, the air conditioning system is switched to fresh air mode at certain time intervals. Such a time control however takes no consideration as to the actual conditions in the passenger compartment of the motor vehicle, that is, for example, how many persons are within the vehicle and the air quality therein.

From DE 197 50 133 C2 a device for monitoring and controlling the CO₂ concentration in the passenger compartment of a motor vehicle is known. Here, in complex and laborious manner, the concentration in the passenger compartment is determined and the excess CO₂-component is eliminated.

DE 197 20 293 C1 describes a device and a process for ventilation of a motor vehicle internal space depending upon corrosive gas. There, in the case that harmful substances or pollutants are detected in the outside air, the air conditioning system is switched from a normal fresh air mode operating condition to a recirculation mode.

A climate control system and a process for controlling thereof is known from DE 198 50 914 A1. Therein, in the cooling circulation, CO₂ is employed as the cooling agent (refrigerant) and a CO₂-sensor is located in the flow down stream of the heat exchanger, which sensor can detect possible damage of the heat exchanger and interrupt air supply to the passenger compartment of the motor vehicle in order to protect the health of the occupants.

SUMMARY OF THE INVENTION

It is the task of the present invention to provide a process for operating a climate control system in an internal space of a motor vehicle, in which the climate control can be operated in its normal condition for recirculating air for saving energy and, in the case that it is necessary, automatically be switched to fresh air mode. It is further the task of the invention to provide a climate control system for a motor vehicle suitable for carrying out this process.

In accordance with the invention this task is solved by the characterizing features set forth in claim 1.

The climate control system switches, upon exceeding a predetermined CO₂-threshold value, which is measured in the passenger compartment of the motor vehicle, into the fresh air ventilation mode. The air quality in the passenger compartment is thus determined by the CO₂ content of the air, and by the switching into the fresh air ventilation mode upon reaching a predetermined threshold it is ensured that the internal space is always supplied in sufficient manner with oxygen-containing fresh air. The CO₂ content thus serves as indicator for the air quality in the passenger compartment of the motor vehicle.

By the conventional operation of the climate control system in the recirculation mode, in particular when cooled air is to be supplied to the passenger compartment, this results in a substantial savings in energy, since the recirculated cabin air requires substantially less cooling than the externally supplied, frequently warmer fresh air, and thus the compressor of the air conditioning system requires less energy. This advantage is however also noticeable in heating operation, since the internal air need not be heated as strongly as the externally supplied, cooler air.

By the inventive coupling of the switching between these two operating modes of the climate control system to the CO₂-level in the passenger compartment of the motor vehicle, a much more constant level of air quality is achievable than the prior time-controlled switching processes. When the motor vehicle is essentially occupied by one person, the climate control system can generally be operated in recirculation mode for a substantially longer period of time than is the case with a time controlled system, which operates based on the presumption of an average, though not maximal, occupancy of the internal space.

A climate control system for a motor vehicle is disclosed in claim 6. Therein a CO₂-sensor is provided in the passenger compartment of a motor vehicle, which triggers or actuates, upon exceeding a CO₂-threshold value, a switching of the control system from recirculation mode to fresh air mode. By means of this inventive climate control system the above described inventive process can be carried out in simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantageous embodiments and further developments of the invention can be seen from the dependent claims as well as from the following embodiment represented schematically in the drawings.

There is shown:

FIG. 1 a motor vehicle with an inventive climate control system; and

FIG. 2 an enlarged representation of the climate control system of FIG. 1

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 a motor vehicle 1 is shown, which includes a passenger compartment 2, and engine compartment 3 and a trunk 4. In the passenger compartment 2 there is located, in known manner, front seats 5 and back seats 6, of which basically only a single one is represented. In front of the front seat 5 is the dashboard 7 with a steering wheel 8 and an ashtray 9. On the front seat 5 there is provided a console 10, into which an ashtray 11 reachable from the backseat 6 is incorporated.

In known manner a climate control system 12 is provided in the dashboard 7, of which individual components are shown in detail in FIG. 2. Thus the climate control system 12 includes a blower 13, with an evaporator 14 downstream in the flow of air, with the direction of flow shown by arrows. An intake 15 leads to the blower 13, which after evaporator 14 branches into three lines 16, 17 and 18. From this, the first line 16 leads to the windshield 19 of the motor vehicle 1, the second line 17 leads to the vent in the direction of the steering wheel 8 and the third line 18 opens into the foot space 20, which is part of the passenger compartment 2. In not described, however in known manner the occupants of the motor vehicle 1 can influence the channeling of air through the three lines 16, 17 and 18 by means of appropriate actuating elements. The intake 15 to the blower 13 is supplied with air from the foot space 20 for recirculation and also by a fresh air line 22. If the blower 13 intakes air essentially from the recirculation line 21, then it is in the recirculation mode, since the internal space 2 is then essentially supplied by recirculated passenger compartment air. If the intake 15 intakes at least a certain portion via the fresh air line 22, than this case is referred to as the fresh air mode of the climate control system 12. In the fresh air mode it is possible via the intake 15 to also intake a certain amount of recirculated internal air. For the switching between the recirculation line 21 and the fresh air line 22, and in between the recirculation operation and fresh air operation of the climate control system 12, a control element 23 is provided embodied in the present case as a flap or valve, which can be adjusted stepless using an adjustment device 24 embodied as a step motor. Conventionally the climate control system 12 is operated in the recirculation mode, since thereby in particular during supplying of cooler air in the passenger compartment 2 a substantial amount of energy can be saved. The fresh air amount is variable and depends upon the control of the control element 23. As an alternative to the stepless adjustment it is of course also possible to switch between recirculation mode and fresh air mode, in which respectfully only either the recirculation line 21 or the fresh air line 22 is connected with the intake 15.

The control over the climate control system 12 is exercised by a control device 25, which as conventional is located in the engine compartment 3 or in the dashboard 7, however, for space reasons, is shown in the figure outside of the motor vehicle 1. Besides being connected with the adjustment device 24, for the control of which it is provided, the control device 25 is further connected with a CO₂-sensor 26 located in one foot space 20 of the passenger compartment 2, wherein of course any larger number of CO₂-sensors 26 can be provided. The CO₂-sensor 26 measures the CO₂ concentration in the passenger compartment 2 of the motor vehicle 1 and, in the case of exceeding a certain predetermined CO₂ threshold value in the passenger compartment 2, provides a signal to the control device 25, so that this is switched from the previously existing recirculation mode to the fresh air mode. For this, essentially the control element 23 must be moved by means of the actuator or adjustment device 24 from the fresh air line 22 in the direction of the recirculation line 21. In this manner the mode of operation of the climate control system 12 is dependent upon the CO₂ content in the passenger compartment 2 of the motor vehicle 1 and it is ensured that the occupants in the case of exceeding a predetermined CO₂-threshold value are supplied with fresh air. It has been found to be particularly advantageous when this CO₂-threshold value is approximately 800 ppm. Of course, the CO₂-sensor 26 or, as the case may be, the control device 25, can be set to other CO₂-threshold values, when this is considered useful or necessary. In certain cases, for the switching between recirculation mode and fresh air mode, the quality or as the case may be composition of the environmental air can also be taken into consideration.

The control device 25 is further connected with two sensors 27 and 28, which are associated with the ashtrays 9 and 11. As soon as the corresponding ashtrays 9 or as the case may be 11 are opened, this is detected by the sensor 27 or as the case may be 28 and relayed to the control device 25, which subsequently switches via the adjustment device (actuator) 24 and the control element 23 of the climate control system 12 as described above into the fresh air mode. Such a supplemental control of the switching of the climate control system 12 from recirculation mode into fresh air mode in response to the ashtrays 9 and 11 is useful, since during smoking increased amounts of CO, NO_(x), etc. are produced and thus an earlier switching into the fresh air mode is desirable. Of course, in connection therewith, additional ashtrays can be provided with appropriate sensors. Supplementally or alternatively to the sensors 27 and 28, which detect to the opening of the ashtrays 9 and 11, other sensors can also be provided in the passenger compartment 2, with which it can be determined whether smoking is taking place in the internal space 2 of the motor vehicle 1. It can be advantageous to switch completely to the fresh air mode if one of the sensors 27 or 28 is activated. The sensors 27 and 28 can of course also be activated independent of the CO₂ content measured by the CO₂-sensors 26, and switch the climate control 12 into the fresh air mode.

In the described process for operating the climate control system 12 it can be further provided, that during switching into the fresh air mode the fresh air is conveyed primarily along the third line 18 into the foot space 20. Since CO₂ is heavier than environmental air, CO₂ collects primarily in the lower area of the passenger compartment 2 and is displaced more quickly from the internal space 2 by the introduced fresh air, for example via not shown openings leading from the passenger compartment 2 into the trunk space 4.

Since CO₂ is heavier than room air, it is alternatively also conceivable to convey the fresh air via the lines 16 and/or 17 in such a manner that is blown into the face area, without mixing with the CO₂ in the foot space 20.

The CO₂-sensor 26 is also very effective and other sensors can be dispensed with in the case that the cooling agent for the evaporator 14 is CO₂. Thereby a possible leakage of the evaporator 14 can be very quickly detected and the climate control system 12 can be switched off and the blower 13, following switching of the control element 24 to fresh air operation, can possibly also be switched to an elevated or as the case may be maximal blower setting, so that a safety device is provided for the occupants by the CO₂-sensor 26, the control device 25 and the control element 23. In order to accomplish this switching off by the control system 12, as shown in FIG. 2, the evaporator 14 can be provided on the pressure side with an expansion valve 29, which separates the evaporator 14 from the circulation, and which blocks it when the CO₂-sensor 26 detects a CO₂ leakage, or when the CO₂-sensor 26 or as the case may be a control signal is lost, for example following an accident. In FIG. 2 there is further shown a compressor 31 connected via a line 30 with the evaporator 14, in the supply line 32 of which a vacuum valve 33 is provided. This valve 33 serves to switch off the compressor 31 in cases of possible leakage of the evaporator 14. 

1. A process for operating a climate control system in the passenger compartment of a motor vehicle, comprising: operating the climate control system in a recirculation mode in which internal air is recirculated within the passenger compartment or in a fresh air mode in which at least a portion of air supplied to the passenger compartment is fresh air, and wherein operating the climate control system in the recirculation mode, wherein the climate control system (12) is switched into the fresh air mode upon exceeding a predetermined CO₂-threshold value measured in the passenger compartment (2) of the motor vehicle (1).
 2. The process according to claim 1, wherein in response to the opening of an ashtray (9, 11) located within the passenger compartment (2) of the motor vehicle (1) the climate control (12) is automatically switched into the fresh air mode.
 3. The process according to claim 1, wherein the climate control system (12) is operated with CO₂ as coolant.
 4. The process according to claim 1, wherein the CO₂-threshold level is set at 800 ppm.
 5. The process according to claim 1 wherein upon switching into the fresh air mode the fresh air is supplied to the foot space (20) of the motor vehicle (1).
 6. A climate control system for a motor vehicle, which is switchable between a recirculation mode, wherein a internal air is recirculated within the passenger compartment of the motor vehicle, and a fresh air mode, at least a portion of air supplied to the passenger compartment is fresh air, and which includes a compressor, an evaporator and a control device, wherein at least one CO₂-sensor (26) is provided in the passenger compartment (2) of the motor vehicle (1), which CO₂-sensor (26), upon detecting a CO₂ level exceeding a CO₂-threshold value in the passenger compartment (2) of the motor vehicle (1), provides a signal to the control device (25) for switching the climate control system (12) from recirculation mode to fresh air mode.
 7. The climate control system according to claim 6, wherein the CO₂-sensor (26) is located in the foot space (20) of the motor vehicle (1).
 8. The climate control system according to claim 6, wherein in the inner space (2) of the motor vehicle (1) at least one sensor (27, 28) is provided, with which it can be detected whether smoking is occurring within the passenger compartment (2) of the motor vehicle (1).
 9. The climate control system according to claim 8, wherein the at least one sensor (26, 27) is so designed that it detects the opening of an ashtray (9, 11).
 10. The climate control system according to claim 6, wherein the control device (25) is in operative association with an adjustment device or actuator (24), which is provided for adjusting a control element (25) between recirculation mode and fresh air mode.
 11. The climate control system according to claim 6, wherein CO₂ is provided as coolant for the evaporator (24).
 12. The climate control system according to claim 6, wherein the evaporator (14) is provided with an expansion valve (29) for switching off of the evaporator (14).
 13. The climate control system according to claim 6, wherein on the vacuum side the compressor (31) is provided with a valve (33) for switching off of the compressor (31). 